On a compact disc, referred to below simply as CD, which is a standardized optical disc with a diameter of 12 cm, there are recorded audio signals, as digital data converted from analog audio signals.
On a routine CD, there is recorded a musical number as a set of audio data making up the musical number. For example, if a musical number is made up of a lyric and the accompaniment music for this lyric, the lyric and the accompaniment music are recorded as one as a set of audio data.
In an orchestra performed by plural sorts of musical instruments, the performance by the plural sorts of musical instruments is recorded as one as a set of audio data.
In a disc on which the lyric and the accompaniment music therefor have been recorded as one as a set of audio data, it is not possible to select and reproduce only the lyric or the accompaniment music, such that, when only the accompaniment music of a musical number is to be reproduced, the accompaniment music needs to be recorded independently of audio data containing the lyric and the accompaniment music.
Even in case of a disc having recorded thereon as one the performance by the plural sorts of musical instruments as a set of audio data, it is not possible to reproduce the performance by only a certain musical instrument forming an orchestra, such as a piano.